A bicycle, also known as a pedal cycle, bike or push-bike, is a human-powered land vehicle that has two wheels attached to a frame, one behind the other. It is powered by the rider, who uses pedals to create motion by pushing on the ground with their feet. A bicycle can be ridden on roads, pathways and off-road, and is used for recreational and utilitarian purposes. The bicycle is a very efficient means of transport, with relatively low environmental impact, and can be used to cover short distances very quickly.

A bike has many parts, but the most basic are a seat, pedals and handlebars. The cyclist uses their feet to propel the pedals, which are connected to the rear wheel via a chain. When the cyclist shifts gears, they change the ratio of the pedals to the wheel, allowing them to climb hills or descend mountains. A bicycle can be equipped with a variety of tires and brakes, and the most advanced have a number of other accessories.

The invention of the bicycle was a milestone in human history. Although some people claim to have invented the first bicycle, most historians agree that no individual qualifies as the inventor. The first practical bicycle was made in 1817 by Baron Karl von Drais, who built a two-wheeled machine that had to be pushed with the legs like a scooter. The Draisienne, or velocipede, was not an instant success, but by the 1870s major bicycle production had begun in Britain.

There are many different types of bicycles, but the most common are made of steel and have a diamond frame with two triangles of tubing. These tubes fit together to form the main triangle and a top tube, which hold the seat post, saddle, and handlebars. The bottom bracket holds the cranks and chainwheels, and the head tube holds the steering forks. There are also step-through frames, with a lower top tube, and racing bikes, which have more of a drop-down geometry.

Bicycles can be made from many different materials, including low-cost and high-quality steel, aluminum, and chromium-molybdenum alloys. They can be painted or chromed, and some have special coatings to protect them from the elements.

Cycling is a great way to get exercise, but it’s important to wear helmets and other safety equipment while riding, especially on busy streets. Regular cycling can help reduce the risk of heart disease, cancer, obesity, and other health problems. The Shanghai Women’s Health Study, which followed 67,000 women over a decade, found that cycling and walking are associated with lower death rates than inactive lifestyles.